Question

A string is wrapped over the edge a uniform disc and the free end is fixed with the ceiling. The disc moves down, unwinding the string. Find the downward acceleration of the disc.

Answer 1

Correct Answer - B::C
Let the radius of the disc =R
Therefore according to the question and ure
`mg-T=ma`
and the toque about the centre
`=TxxR=1xxalpha`
`rarr TxxR=1/2(mR^2xxa)/R`
`rarr T=1/2 ma`………..2

Putting this value in the equation 1 we get
`rarr mg-1/2ma=ma`
`rarr mg=3/2ma`
`implies a=(2g)/3`